Selection – How Evolution Occurs

The E. coli • Where is it from? • What is model 1 showing about the E. Coli?

How Populations Change Graph of Population of Peppered moths

Peppered Moths

The Moths What is happening? • Changes in the frequency of light and dark moths over time • What is happening to the moths? - behavior of moths in the day (resting on tree trunks) - predation • Why the change in frequencies? What do you predict regarding the frequencies of the light and dark moths after the passage of the clean air acts in the mid 1950’s?

Genetic Variation

Pressure from the environment

1) All Species - produce excessive numbers of offspring 2) Variation - in species leads to some organisms being more successful than others. a) Organisms - that are more successful are considered more “fit”

Genetic Diversity

Pressure from the Environment leads to differential reproductive success

Natural Selection in Action Two Key Things: 1) Natural Selection is a screening process pesticide did not create resistance 2) Natural selection favors those characteristic that fit a specific current local environment

Evolution Can Happen in Lifetime

Sickle cell anemia • Genetic disorder – Inherit one gene from each parent (SCA) – Inherit one gene from only one parent (SC carrier) Seems not to confer an advantage, or does it? • Having sickle cell anemia can shorten life • But also…. • Sickle cells are hard and C shaped • Get stuck in blood vessels • Painful/Acute Chest Syndrome/Stroke

Frequency of sickle cell carriers and Malaria Parasite